Refrigerating apparatus



July 19, 1938. R, SMITH 2,124,239

REFRIGERATING APPARATUS Filed Dec. 24, 1934 INVENTOR.

ATTORNEY,

Patented July 19, 1938 UNITED STATES REFRIGERATING APPARATUS Rolf M. Smith, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware 7 Application December 24, 1934, Serial No. 758,871

Claims. (01. 230-207) This invention relates to refrigerating apparatus and more particularly to a novel motorcompressor unit of the hermetically sealed type for use in a refrigerating system.

It is common practice in the refrigerating art to provide a motor-compressor unit which is completely enclosed in a hermetically sealed casing within which refrigerant and lubricant for the compressor are circulated, one of the principal, advantages of this class of construction being that the use of a stuffing box or other shaft seal is avoided. In motor-compressor units of this type, however, certain problems are incurred in connection with the maintenance of proper lubrication for the compressor which are peculiar to this type of unit since the hermetically sealed casing makes the compressor mechanism inaccessible for servicing and necessitates great care in insuring that all parts of the mechanism will operate properly for the life of the machine. In refrigerators intended for household use, present-day standards also require that noise of operation of the motor-compressor unit be reduced to a value which is substantially imperceptible and it has been found that particularly with units employing a rotary-compressor, the maintenance of an unfailing supply of substantially undiluted lubricant for feed to the compressor is a major factor in insuring quiet operation.

It is an object of the present invention, therefore, to provide a motor-compressor unit preferably of the hermetically sealed type in which provision is made for insuring the maintenance of an unfailing supply of lubricant for the moving parts of the compressor.

Another object is to provide a compressor of this character which will be quiet in operation throughout its useful life.

It is also an objectto provide a mechanism of the character described which is simple, reliable in operation and which is not only inexpensive in construction, but which also involves the addition of no wearing parts.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

The figure is a vertical cross section of a portion of a motor-compressor unit embodying the present invention, and shows diagrammatically the elements of a complete refrigerating system.

Referring now to the drawing, there is shown a motor-compressor unit l0 having an outlet I2 from which compressed refrigerant is adapted to be delivered to a condenser l4 by a conduit I6. The condenser l4 collects liquefied refrigerant in a receiver portion l8, whence it is delivered by a combined restrictor and liquid line 20 to a second restrictor 22 for expanding refrigerant into an evaporator 24. A conduit 26 delivers expanded refrigerant to the inlet 28 of the compressor l0, after passing in heat exchange relation'with the liquefied refrigerant in line 20. A thermostatic switch 30 controls the starting and stopping of the motor-compressor unit ill in accordance with the temperature of the evaporator 24. The parts thus far described are representative of the conventional elements of a, refrigerating system and the disclosure thereof is intended as illustrative of but one of the many types of apparatus with which the present invention may be employed. v

The motor-compressor unit In comprises a housing 32 having an open bottom which is closed by a base member 34 which in turn is welded to the housing 32 at 36, to provide a hermetically sealed chamber 38. Within the chamber 38 in the upper portion thereof, there is mounted an electric motor comprising a stator 40 and a rotor 42. A hollow stationary shaft 44 is located centrally of the housing 32 and mounted rigidly, as by welding, in the base 34. A socket member 46 secured to the top of the housing 32 positions the upper end of the shaft 44. A hollow compressor drive shaft 48 is journaled on the shaft 44 carrying at its upper portion the rotor 42, while at the lower end, there is provided an eccentric journal 50. Secured to the base 34 is a compressor body member which may comprise a pair of bottom plates 52, a cylinder member 54,

-' a valve cover plate 56 and a retainer plate 58.

The parts 52 through 58 inclusive are rigidly secured together and to the base 54 and provide a cylindrical compression chamber 60 which is concentric with the axis of the shaft 44. The

cylinder member 54 is provided with a radial slot, not shown, for receiving a divider block in the well known manner. Mounted within the compression chamber 60 is a cylindrical impeller 62 which is journaled on the eccentric journal 50 and is adapted to revolve in the compression chamber 60 without rotating. The customary divider block, not shown, is provided for dividing the chamber 60 into a compression space and a suction space. The inlet connection 28 communicates with the suction space immediately adjacent one side of the divider block, while a discharge orifice 64 communicates with the comfor charging the unit with liquid refrigerant and lubricant. Connections to the motor are brought through the base 34 by the sealed lead-in connections I2.

In order to provide for a. constant supply of lubricant tothe running surfaces of the compressor, the following mechanism is provided. A cover or can member I4 is attached to the compressor body member and sealed thereto at the top by a gasket I8. The can I4 has a downwardly depending skirt 18 which embraces the compressor body member. At its top, the can member I4 is provided with an upwardly directed neck portion 88 and an inwardly turned top portion 82 extending fairly close to the rotary shaft 48. Secured to the top of the rotor 42 is a lubricant collecting reservoir and feeding member or bowl member generally designated as 84 which is secured to the top surface of the rotor 42 and which rotates therewith. The member 84 has a flat base portion 88 which is sealed to the rotor 42, and a substantially semi-annular collector portion 88 extending above the base portion 88. At the upper edge of the portion 88, the member 84 is formed with a flat frusto-conical portion 98 which terminates at its outer periphery in a second semi-annular collector portion 92. The size of the two semi-annular portions 88 and 92 is carefully predetermined as to the volume of lubricant that will be retained in each portion under idle and running conditions. A lubricant feeding duct 84 is formed in the rotor 42 adjacent the shaft 48 andhas its upper end positioned within the collector portion 88 so that the entrance to the duct 94 lies a predetermined distance above the top surface of the rotor and above the end of the shaft 48, as well as a predetermined distance radially inwardly from the outer periphery of the semi-annular portion 88. After assembly of the unit, a charge of oil or other lubricant is placed in the chamber 38 through the plug 18 sufficient to maintain a level in the chamber 38 such as indicated by the line I88. Lubricant feed screws are provided for insuring lubrication of the bearings associated with the shaft 48 and may comprise a. downwardly directed helical,

groove I82 on the eccentric journal, 58 and an upwardly directed helical groove I84 on the lower journal of the shaft 44. A slot I88 is formed at the central portion of the uppermost plate 52 to frovide a lubricant passage from the eccentric peller 82 to revolve within the compression space 88, drawing in gaseous refrigerant through the inlet connection 28 and discharging it through the exhaust orifice 84, all as is well known in compressors of the type described. The body of lubricant in'the lower portion of thechamber 38 is drawn underthe lower edge of the skirt I8 of the can 14 and up between cylinder 54 andskirt I8 by leakage between cylinder 54 and plate 58 from the suction side of the compression chamber and is fed to the compression chamber88 at a very slow rate of seepage through the running joint at the divider block. This constitutes the only direct feed of lubricant to the compression chamber 88 from the main body of lubricant in the chamber 38. The mixed gaseous refrigerant and lubricant discharged through the flapper valve 88 is somewhat separated in the chamber formed by the upper portion of can member I4, the lubricant collecting on top of the compressor body and the This substantially undiluted lubricant is fed to the compressor through the running surface between the impeller 82 and the valve plate 58 and is also fed to the bearings of the compressor, first entering the feed groove I82 to be forced downwardly through the eccentric journal, then passing through the groove I86 to be fed upwardly by the helical groove I84 to lubricate the lower and upper journals on the shaft 44. Some lubricant also passes to the compressor from the groove I88 between the impeller 82 and the base plate 52. The lubricant discharged from the upper bearing on the shaft 44 is trapped within the collector portion 88 and while the device is running it is maintained by centrifugal force in a sort of annular body indicated by the dotted line I88. The entrance to the duct 94 is so positioned that lubricant from this annular body will be drained downwardly to replenish the supply on top of the compressor body. It will be seen, therefore, that the supply of lubricant on top of the compressor body is fed from two sources, namely: from the duct 94 and from separation of the lubricant from the mixture discharged through the flapper valve 88. The size of the duct 94 is such that during normal operation, the level of lubricant above the compressor body is maintained substantially at the dotted line II8. Any excess lubricant collected in the semi-annular portion 88 will pass off the upper edge thereof and by centrifugal force will be directed along the conical portion 98 to collect in the semi-annular collector portion 92 where another' 1 substantially annular body of lubricant is maintained under centrifugal force which is indicated by the dotted line I I 2. After this annular body of lubricant has been collected in the portion 92 any further excess of oil traveling up the cone 98 will be thrown off the upper edge of the collector member 84 to drain back to the main body of lubricant in the chamber 38. When conditions at the evaporator 24 are such that refrigeration is no longer needed, the switch38 is opened and the motor-compressor unit stops. As soon as the unit stops, the centrifugal force maintaining the two annular bodies of lubricant in the portions 88 and 92 disappears, with the result that both bodies of lubricant drain to the chamber above the upper end of shaft 48 The collector 84 is so positioned that the quantity of lubricant available fills the chamber formed by the portion 88 to a level substantially above the duct 94. The quantity of lubricant which is thus above the duct 94 drains to the chamber above the compressor body and raises the level therein to a point above the flapper valve 88, thus acting to seal the valve during the idle period. In addition, this increased supply of lubricant above the compressor body assures a copious supply of lubricant for the bearing surfaces of the compressor when the unit again starts. Upon restarting the unit, the quantity of lubricant remaining on top of the shaft 48 up to the level of the entranceto the duct 94 is again subjected to centrifugal force and thrown against the side walls of the portion'88 where it can immediately begin feeding through the duct 94 to the body of refrigerant above the compressor body. Thus, not only is an extra supply of lubricant maintained above the compressor before starting the unit, but also the replenishing of that supply of lubricant is begun almost immediately after the unit starts so that the possibility of starving any of the surfaces in the compressor requiring lubrication is eliminated. The member 84 serves an additional function in that it has been found that lubricant intralned in the compressed refrigerant tends to collect on the bottom surface of the top wall of the housing 32 and drains to the lowest portion thereof which is adjacent the center. Inasmuch as the conical portion 90 of the member 84 is positioned immediately below the lowest portion of the top wall of the housing 32, the lubricant dripping therefrom is collected on the conical portion 90 and insures the maintenance of a full supply of lubricant in the semi-annular collector portion 92 at all times while the unit is running. In addition, the member 84 serves to maintain the body of compressed refrigerant in constant rotary motion, and since the outlet from the chamber 38 is located in the center, a complete centrifugal separation of the lubricant from the refrigerant is effected before the refrigerant enters the passages 68.

It has been found that considerable noise in compressors of the present type has heretofore been caused by lack of maintenance of a sufficient supply of lubricant for these surfaces particularly at starting, which lets the lubricant film break down and permits a slight oscillating action of the impeller 62 about a horizontal axis. The resultant noise is therefore avoided by the present invention. Thus, the present invention provides for continued satisfactory operation of a hermetically sealed motor-compressor unit throughout substantiallyv its useful life and insures quiet operation thereof by maintaining a supply of concentrated, substantially undiluted lubricant for feeding to all the working surfaces of the compressor.

It will be understood that the particular shape of the collector portions 88 and 92 may be varied as desired, and that wherever in the appended claims the expression semi-annular is used, it is to be construed as including any shape capable of collecting and holding lubricant under centrifugal force in the manner described.

While the form of embodiment of the present invention as herein described constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a hermetically sealed motor-compressor unit, the combination of a vertical shaft, a compressor, a motor, anda bearing associated with said shaft, 2. main body of lubricant, means for feeding lubricant upwardly from said main body.

through said bearing, means for collecting the Inbricant overflowing from said bearing above said main body, and means for feeding a portion of the collected lubricant to the compressor independently of said main body at a predetermined rate, means for collecting the remainder of the lubricant overflowing said first collecting means and for storing a predetermined quantity thereof under centrifugal force during operation of the unit, and, means whereby the lubricant thus stored may feed by gravity to the compressor when the unit stops.

2. In a hermetically sealed motor-compressor unit, the combination of a vertical shaft, a compressor, a motor, and a bearing associated with said shaft, a main body of lubricant, means for feeding lubricant upwardly from said main body through said bearing, means for collecting the lubricant overflowing from said bearing above said main body, and means for feeding a portion of the collected lubricant to the compressor independently of said main body at a predetermined rate, said collecting means and said feeding means being relatively proportioned and positioned so that a supply of lubricant is stored in said collecting means while the unit is idle, means for collecting the remainder of the lubricant overflowing said first collecting means and for storing a predetermined quantity thereof under centrifugal force during operation of the unit, and means whereby thelubricant thus stored may feed by gravity to the compressor when the unit stops.

3. In a hermetically sealed motor-compressor unit, the combination of a casing, a compressor in the lower portion of the said casing, a motor above said compressor in said casing, a driving connection between said compressor and motor including a vertical drive shaft and bearing means therefor, a first body of lubricant in said casing, a lubricant reservoir above said first body of lubricant for lubricating a portion of said compressor, means for supplying lubricant to said bearing means, a rotating cup receiving lubricant from said bearing means and retaining lubricant by centrifugal action during normal operation of said compressor, and means forming a rotating substantially vertical tube from said cup to said reservoir for feeding lubricant to said reservoir during rotation.

4. In combination, a compressor having s. rotary shaft projecting upwardly therefrom, a 111- bricant supply pocket in the upper side of said compressor, a bowl member carried by said shaft above said pocket and rotating with said shaft,

-means for supplying lubricant to said bowl, said bowl member having an inturned rim preventing a portion of the lubricant supplied to the bowl from being thrown out during rotation of said bowl, and a conduit leading from a point adjacent the bottom of said bowl to said lubricant supply pocket whereby when said compressor stops lu-. bricant retained in said bowl drains into said supply pocket.

5. In combination, a. compressor, a motor for said compressor, a rotary drive shaft between said motor and compressor, a lubricant reservoir carried by said shaft adjacent its upper end, means for supplying lubricant to said reservoir during operation of said compressor, and a lubricant passage leading from said reservoir to said compressor, the opening in the reservoir to said passage being spaced from the outer periphery of said reservoir whereby centrifugal force prevents lubricant located between said opening and the outer periphery of said reservoir from entering said passage while said shaft rotates, said passage and said reservoir being so constructed and arranged that when said shaft stops rotating substantially all of the lubricant in said reservoir drains through said passage.

ROLF M. SMITH. 

